[meteorite-list] Tunguska Catastrophe: Evidence Of Acid Rain Supports Meteorite Theory

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Tue, 15 Jul 2008 20:23:58 -0400
Message-ID: <qqfq74h8t0o7088v662corl0f30ed712oo_at_4ax.com>

http://www.sciencedaily.com/releases/2008/07/080715103956.htm

Tunguska Catastrophe: Evidence Of Acid Rain Supports Meteorite Theory

ScienceDaily (July 15, 2008) ? The Tunguska catastrophe in 1908 evidently led to
high levels of acid rain. This is the conclusion reached by Russian, Italian and
German researchers based on the results of analyses of peat profiles taken from
the disaster region. In peat samples corresponded to 1908 permafrost boundary
they found significantly higher levels of the heavy nitrogen and carbon isotopes
15N and 13C.

The highest accumulation levels were measured in the areas at the epicentre of
the explosion and along the trajectory of the cosmic body. Increased
concentrations of iridium and nitrogen in the relevant peat layers support the
theory that the isotope effects discovered are a consequence of the Tunguska
catastrophe and are partly of cosmic origin. It is estimated that around 200,000
tons of nitrogen rained down on the Tunguska region in Siberia at that time.

"Extremely high temperatures occurred as the meteorite entered the atmosphere,
during which the oxygen in the atmosphere reacted with nitrogen causing a build
up of nitrogen oxides," Natalia Kolesnikova told the Russian news agency RIA
Novosti on last Monday. Mrs. Kolesnolova is one of the authors of a study by
Lomonosov Moscow State University, the University of Bologna and the Helmholtz
Centre for Environmental Research (UFZ), which was published in the journal
Icarus in 2003.

The Tunguska event is regarded as one of the biggest natural disasters of modern
times. On 30 June 1908 one or more explosions took place in the area close to
the Tunguska River north of Lake Baikal. The explosion(s) flattened around 80
million trees over an area of more than 2000 square kilometres. The strength of
the explosion is estimated to have been equivalent to between five and 30
megatons of TNT. That is more than a thousand times as powerful as the Hiroshima
bomb.

This almost unpopulated region of Siberia was first studied in 1927 by Professor
Leonid A. Kulik. There are a number of different theories about what caused the
catastrophe. However, the majority of scientists assume that it was caused by a
cosmic event, such as the impact of a meteorite, asteroid or comet. If it had
exploded in the atmosphere just under five hours later, St. Petersburg, which
was the capital of Russia at that time, would have been completely destroyed
because of the Earth?s rotation.

In two expeditions in 1998 and 1999, Russian and Italian researchers took peat
profiles from various locations within the Siberian disaster area. The type of
moss studied, Sphagnum fuscum, is very common in the peat material and obtains
its mineral nutrients exclusively from atmospheric aerosols, which means that it
can store terrestrial and extraterrestrial dust. Afterwards, the samples were
analysed in laboratories at the University of Bologna and the Helmholtz Centre
for Environmental Research (UFZ) in Halle/Saale.

Among other things, the UFZ specialises in isotope analyses of sediments,
plants, soil and water and it was asked to help by the team of Moscow
researchers led by Dr Evgeniy M. Kolesnikov. Kolesnikov, who has been
investigating the Tunguska event for 20 years, has been to Leipzig University
and UFZ twice as a guest researcher with the help of the German Research
Foundation (DFG) to consult with the isotope experts.

"The levels of accumulation of the heavy carbon isotope 13C measured right on
the 1908 permafrost boundary in several peat profiles from the disaster area
cannot be explained by any terrestrial process. This suggests that the Tunguska
catastrophe had a cosmic explanation and that we have found evidence of this
material," explains Dr Tatjana B?ttger of the UFZ. Possible causes would be a
C-type asteroid like 253 Mathilde, or a comet like Borelly.
Received on Tue 15 Jul 2008 08:23:58 PM PDT